Burns,

Just practical/experience sharing.

Actually it does matter using a computer aided tuning if both in a QSO using same e.g. using SatPC32 works very well and may be only slight adjustment of RIT or XIT to keep you in sync through the whole pass of the bird. 

Manual tuning also possible and very often used but one need much more skills and mental calculation to keep on a common QRG.

Inverted make it easier for manual operations.

My one cent input.

73

Jean Marc (3B8DU)

On Aug 29, 2022, at 9:10 PM, Burns Fisher <wb1fj-bb@fisher.cc> wrote:

Ok, let me try this:

I'm not 100% sure what you mean by "tune to the linear birds", but I can guess.  Ask again if this answer does not help.  A linear satellite has a 20 to 40kHz range in the uplink band where anything it receives is sent to the same (but usually inverted) location in the downlink band.  If you want to hear yourself or anyone responding to you, you must tune your receive frequency to match your transmit frequency.   It would be nice if such satellites had an exact local oscillator so that you could get the tx and rx frequencies all set ahead of time, but these oscillators do drift.  That means you generally have to "tweak" the tuning a bit to get the receive tuned so that you hear yourself clearly.    Is that what you are asking?

As to inverting/doppler, yes it does say that in the amateur exam (Extra, I think).  I have to say, I thought I understood this, but everytime I started to write about it, I realized "no, that is not right".  So for now, I think I'll just say that it does not really matter if you have computer-aided tuning.

73,

Burns WB1FJ

On Mon, Aug 29, 2022 at 12:35 PM Calvin McDonald <7ndel3fr@gmail.com> wrote:

I have searched a little and have failed to find the info I'm curious about, so I will ask here.? Can someone point me at a source that will explain why we have to tune to the linear birds and also why inverting transponders work better for Doppler compensation as opposed to non-inverting?
Thanks

-----------------------------------------------------------

Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available
to all interested persons worldwide without requiring membership. Opinions expressed
are solely those of the author, and do not reflect the official views of AMSAT-NA.
Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/

View archives of this mailing list at
https://mailman.amsat.org/hyperkitty/list/amsat-bb@amsat.org
To unsubscribe send an email to amsat-bb-leave(a)amsat.org
Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org

-----------------------------------------------------------

Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available
to all interested persons worldwide without requiring membership. Opinions expressed
are solely those of the author, and do not reflect the official views of AMSAT-NA.
Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/

View archives of this mailing list at
https://mailman.amsat.org/hyperkitty/list/amsat-bb@amsat.org
To unsubscribe send an email to amsat-bb-leave(a)amsat.org
Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org